Non-mechanical tracking devices, such as computer mice, are rapidly growing in popularity worldwide. Many of these non-mechanical tracking devices utilize optical navigation technology that measures the changes in position of the non-mechanical tracking devices by optically acquiring sequential surface images and mathematically determining the direction and magnitude of the movement.
As an example, in a non-mechanical tracking device such as an optical mouse, optical navigation technology involves capturing an image and then analyzing and tracking the motion of microscopic texture or other features on a surface under the optical mouse. In general, these types of optical mice depend on tracking surface detail and most work surfaces are microscopically textured with such tracking surface detail. When these surface textures are illuminated by a light source such as a light emitting diode (“LED”), a pattern of highlights and shadows is revealed. Optical mice then “watch” these surface details move by imaging them onto navigation integrated circuits (“navigation ICs”).
As an example, in FIG. 1, a block diagram 100 of an example of a known implementation of an optical navigation device 102 above a navigation surface 104 is shown. The optical navigation device 102 may be a non-mechanical tracking device such as an optical mouse. Generally, optical navigation technology involves capturing an image on the navigation surface 104 and then analyzing and tracking the motion of microscopic texture or other features on the navigation surface 104 under the optical navigation device 102. Thus, the optical navigation device 102 depends on tracking the navigation surface 104 detail because most navigation surfaces 104 are microscopically textured. When these surface textures are illuminated 106 by a light source such as an LED in an emitter module 108, a pattern of highlights and shadows is revealed at a point of illumination 110 on the navigation surface 104. The optical navigation device 102 then “watches” the surface details of the navigation surface 104 move by imaging 112 the navigation surface 104 details at the point of illumination 110 onto a detector module 114 in the optical navigation device 102. The detector module 114 may be part of a navigation integrated circuit (“IC”) 116 located within the optical navigation device 102. The navigation IC 116 may also include a navigation engine 118 where the navigation engine 118 is a device capable of receiving imaging information from the detector module 114 and, in response, determining the position of the optical navigation device 102.
The optical navigation device 102 may also be implemented as a laser optical navigation device. As an example of a laser optical navigation device, a vertical cavity surface-emitting laser (“VCSEL”) may be utilized as the light source in the emitter module 108 to illuminate the point of illumination 110 on navigation surface 104. A VCSEL is a semiconductor micro-laser diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer, and offers advantages in both performance and cost when compared to other semiconductor lasers such as edge-emitting lasers. The VCSELs are cheaper to manufacture in quantity because VCSELs may be fabricated efficiently using standard microelectronic fabrication methods, allowing integration of VCSELs on-board with other components without requiring pre-packaging. Additionally, VCSELs are easier to test, and are more efficient. Moreover, VCSELs require less electrical current to produce a given coherent energy output and emit a narrow, more nearly circular beam than traditional edge emitters.
In FIG. 2, a cross-sectional side view of an example of an implementation of a known laser optical navigation device 200 that utilizes a VCSEL is shown above a navigation surface 202. The laser optical navigation device 200 may include a base plate 204 to which is attached a lens 206. In this implementation, the emitter module 108 of FIG. 1 is VCSEL 208 that is attached to and aligned with the lens 206 by VCSEL assembly clip 210. The VCSEL 208 has attached to it a VCSEL printed circuit board (“PCB”) 212, which may be customer-supplied and is programmable dependent on the application. The equivalent of the detector module 114 of FIG. 1 is optical sensor 214 that is in signal communication with sensor PCB 218.
In an example of operation, the VCSEL 208 may emit emitted optical radiation 220 at the navigation surface 202 at a predetermined angle. The emitted optical radiation 220 is then reflected by the navigation surface 202, resulting in reflected optical radiation 222 that passes through the sensor aperture 216 of the lens 206. After the emitted optical radiation 220 is focused by the sensor aperture 216, it is received by the optical sensor 214. The optical sensor 214 may include an image acquisition system, a Digital Signal Processor (“DSP”), a two channel quadrature output, and a four-wire serial port. An example of such an optical sensor 214 is the Avago Technologies' ADNS-6000 optical sensor. Output signals from the optical sensor 214 may be read by a microcontroller (not shown) to obtain any horizontal and vertical motion information resulting from movement of the laser optical navigation system 200 relative to the navigation surface 202.
The emitter module, in this case, the VCSEL 208, the lens 206, the optical sensor 214, the sensor aperture 216, and the sensor PCB 218 may be considered as an optical pipeline for image acquisition. Unfortunately, the optical navigation system 200 has only a single image-acquisition optical pipeline that is capable of acquiring images for correlation purposes. There are, however, applications that require sensing the movement of a device relative to two or more different surfaces. One approach to meeting this requirement is to use two or more optical navigation sensors. This approach, however, is inefficient and costly.
Thus, there is a need for an optical navigation system and method that is capable of measuring the movement of two or more surfaces using a single integrated device capable of processing images reflected from the two or more surfaces.